In recent years, the number of patients with cardiac infarction, cerebral infarction or the like is increasing. These infarctions are caused by interruption of blood flow due to obstruction or stenosis of a blood vessel, which occurs by deposition of thrombi, plaques or the like on the vascular wall. In general, for treatment of a site of obstruction or stenosis in a blood vessel, percutaneous treatment by balloon angioplasty or stenting using a balloon catheter or a stent is carried out.
In treatment by balloon angioplasty, an inflatable balloon at the distal end portion of a balloon catheter is expanded at a site of obstruction or stenosis in a blood vessel to secure the intravascular lumen and to thereby maintain the blood flow. However, when a blood vessel is expanded by the balloon, thrombi or plaques deposited on the vascular wall might be unexpectedly released, and such a substance might then be carried away by blood flow to cause obstruction of a peripheral thin blood vessel, resulting in infarction.
In treatment by stenting, a stent composed of a material such as nitinol or cobalt alloy having the shape of an almost cylindrical tube or mesh sleeve is permanently or temporarily introduced to a site of stenosis in a blood vessel to secure the intravascular lumen and to thereby maintain blood flow. However, similar to balloon angioplasty, when the stent is placed in a blood vessel, thrombi or plaques deposited on the vascular wall might be unexpectedly released, causing infarction.
An endovascular treatment aiding device to be used in combination with a treatment device such as a balloon catheter or a stent has been developed to avoid such a risk. The endovascular treatment aiding device is percutaneously placed in a site which is more peripheral than the lesion where the balloon catheter or the stent is to be placed, and used to capture thrombi or plaques released from the vascular wall.
As such an endovascular treatment aiding device, one having a structure containing: a shaft with an outer diameter which allows the shaft to pass through the guide wire lumen of a treatment device such as a balloon catheter; and a filter fixed in the distal side of the shaft has been reported. The filter has a mesh-shaped or sheet-shaped membrane composed of a polymer material on which a plurality of openings are formed, and has a shape in which the peripheral vessel side, that is, the distal side, is closed, and the central vessel side, that is, the proximal side, is open (JP 2008-35923 A).
By this, during treatment using a treatment device such as a balloon catheter, thrombi or plaques released and carried away from the vascular wall can be captured by the filter constituting a part of the endovascular treatment aiding device placed in the peripheral side without blocking blood flow.
When such an endovascular treatment aiding device is used, the endovascular treatment aiding device, with its filter closed, is contained in a delivery sheath and delivered to the site where the device is to be placed, which is located more peripheral than the lesion. After delivery, the filter is released by removal of the delivery sheath to the outside of the body. This causes self-expansion of the opening section of the filter, thereby allowing close contact of the opening section to the vascular wall. When the endovascular treatment aiding device is to be retrieved, a retrieval sheath is delivered along the endovascular treatment aiding device, and the filter containing thrombi or plaques is stored inside the retrieval sheath, followed by its removal to the outside of the body.
As an endovascular treatment aiding device that enables reduction of leakage of thrombi, plaques or the like by increasing adhesion to the vascular wall, an endovascular treatment aiding device comprising a ring-shaped member formed with a superelastic metal provided in the opening section of the filter, wherein, by folding the ring-shaped member by bundling of a supporting member that acts as a support between the shaft and the ring-shaped member, the filter can be folded into a bag shape, has been reported (JP 4073869 B).
When such an endovascular treatment aiding device is placed in a blood vessel, the living body recognizes it as a foreign substance, and blood coagulation reaction proceeds to cause formation of a thrombus. Therefore, antithrombogenicity is required for the device. In view of this, endovascular treatment aiding devices to which antithrombogenic compounds are given have been reported (WO 2003/084437, WO 2008/005898 and WO 2013/059069).
However, in the endovascular treatment aiding device described in JP '923, contacting with the stent may occur during delivery of a retrieval sheath because of the thick diameter of the distal end of the retrieval sheath so that there is a possibility that the retrieval sheath cannot be delivered to the filter. Moreover, since the opening section of the filter does not have a ring shape, its adhesion to the vascular wall is insufficient so that there is a possibility of leakage of thrombi, plaques, or the like during treatment using a balloon catheter or the like.
In the endovascular treatment aiding device described in JP '869, a sudden diameter transition like step is generated between the opening section of the filter and the shaft when the filter is in the closed state. Therefore, when the endovascular treatment aiding device is used at the same time as a treatment device such as a balloon catheter or a stent, there is a possibility that the end portion of the stent or the distal end portion of the guiding catheter is caught in the step generated between the opening section of the filter and the shaft, and a part of the filter is turned up, leading to leakage of the thrombi or the plaques captured.
Although WO '437, WO '898 and WO '069 describe giving of antithrombogenic compounds to endovascular treatment aiding devices, there is no description on the optimal types and combinations of the antithrombogenic compounds.
That is, conventionally, there is no known endovascular treatment aiding device that solves both of the two problems, that is, there is no known endovascular treatment aiding device that, during its retrieval, securely allows delivery of a retrieval sheath to the filter, and can prevent the filter with captured thrombi or plaques from being caught in a device such as a stent or a guiding catheter.
It could therefore be helpful to provide an endovascular treatment aiding device that, during its retrieval, securely allows delivery of a retrieval sheath to the filter, and can prevent the filter with captured plaques or the like from being caught in a treatment device such as a stent or a guiding catheter.